(1) Field of the Invention
The present invention relates to a system and method for video editing in which a video is divided into shots and after video effects such as wipes have been applied, the shots are rearranged.
(2) Description of the Related Arts
In a known video editing system, editing is performed, for example, in such a way that desired shots are selected from an original source (that is, one roll of video tape including pictures taken by a video camera etc.) and dubbed in a master tape.
In such a case, by the use of a transitional television and film technique such as wipes or dissolves, a video effect is achieved in a joint between one shot and another on the master tape. "Wipes" mentioned herein are transitional techniques in which: when two shots A and B continue in time, the transition therebetween is arranged such that the preceding shot A is partly broken away and the following shot B is projected in the broken-away part. The preceding shot A fades out as the following shot B fades in so that the former is gradually replaced by the latter.
"Dissolves" are such transitional techniques that the picture elements of the preceding shot A and those of the following shot B in the same locations are combined at a specified rate, thereby composing the picture elements in the above locations. The rate changes as time elapses so that the shot A is gradually replaced by the image of the shot B.
In order to perform shot transition with a passage of time such as wipes or dissolves, the shot A and the shot B need to be reproduced on different channels while they are being recorded on the master tape.
Therefore, there has been conventionally used such a technique that the shot A and the shot B are recorded on a roll tape for channel A and a roll tape for channel B respectively, after being taken from an original source and these shots are reproduced from the respective roll tapes with a predetermined timing.
With reference to FIG. 1, the structure of a prior video editing system will be hereinafter described. In FIG. 1, if Reference numeral 11 denotes an effects generator unit comprised of two channels A and B, for applying a video effect such as a wipe to video data entered in each input channel and then releasing the video data as output. The output of the effects generator unit 11 is recorded on a master tape. Reference numeral 12 denotes a video storage unit for a channel A which corresponds to the aforementioned A-channel roll tape. Reference numeral 13 is a shot information storage unit for the channel A. Shot information consists of frame Nos. which designate the start and termination of a shot stored in the A-channel video storage unit 12. Reference numeral 14 is a B-channel video storage unit which corresponds to the aforementioned B-channel roll tape.
Reference numeral 15 denotes a B-channel shot information storage unit which has the substantially same structure as the A-channel shot information storage 13, and in which shot information from the channel B is stored. Reference numeral 16 denotes a channel allocation unit which includes information on the reproducing order of shots from the channel A and the channel B and information on the width of each transition (i.e., the number of frames to be used for each transition). This channel allocation unit 16 receives shot information on each shot of each channel and prepares shot order information for the channel A and for the channel B respectively. The shot order information consists of frame Nos. on the master tape, by which the start and termination of reproduction of each shot from the channels A and B are indicated. Reference numeral 17 denotes an A-channel shot reproduction unit, and Reference numeral 18 denotes a B-channel shot reproduction unit. These units 17, 18 reproduce shots sent from the A-channel video storage unit 12 and the B-channel video storage unit 14 respectively at a timing which is determined in compliance with the respective shot order information (from the channel allocation unit 16) for the channel A and for the channel B, and then send the reproduced shots to the effects generator unit 11.
In the system having the above arrangement, the editor must preliminarily perform the following steps before editing can be automatically performed. Specifically, the user must (1) select particular shots to be taken out of the original source and (2) determine which storage unit 12 video storage unit 14 (12 or 14) will be used for storing each particular shot. Video data in the two video storage units 12, 14 are then reproduced in an order predetermined by the channel allocation unit 16, and the effects generator unit 11 creates wipes to the video data.
Here, suppose that the shots shown in FIG. 2 are linked using the above video editing system. FIG. 2 shows the case in which Shot A is firstly reproduced and Shot B is then reproduced being linked to Shot A by a wipe, and thereafter, Shots C and D are reproduced in this order being linked by a wipe.
According to step (2) above, the user must decide whether a selected shot is allocated to the channel A or the channel B. In the case shown in FIG. 2, since each shot is linked by a wipe, if Shot A is allocated to the channel A, Shot B, Shot C, Shot D will be allocated to the channel B, the channel A and the channel B respectively.
After this step (2), the user must determine whether the contents of each shot are stored in the proper video storage units 12, 14 (which corresponds to the channel to which the shot has been allocated). For example, if the contents of Shot C are not stored in the A-channel video storage unit 12 but stored in the B-channel video storage unit 14, the contents must be copied from the video storage unit 14 to the video storage unit 12 prior to starting of editing.
It is not until the completion of the above-described preparation that the channel allocation unit 16 prepares a link order as shown in FIG. 3, in which the shots are arranged in order in relation to the channels A and B. The link order is then released to the shot reproduction units 17, 18 to obtain a desired result.
The prior video editing system, however, has the disadvantage that since the user has to allocate, prior to starting of actual editing operation, each shot to be taken from the original source to the A-channel video storage unit 12 or the B-channel video storage unit 14 according to an editing plan imaged by the user, the operation for copying shots of the original source into the video storage units 12, 14 is required and, furthermore, it is very difficult to change the allocation once shots are allocated.
For example, such necessity often arises after completion of allocation that the link order of shots is altered by relocating shots after seeing an editing result or new shots are inserted into existing shot sequence. In such cases, the following troublesome operations become necessary: A shot to be relocated is copied from either one of the video storage units 12, 14 into the other while rewriting the corresponding information stored in the shot information storage unit 13 or 15; or all the shots located after an insert position are relocated between the video storage units 12, 14 while rewriting the corresponding information stored in the shot information storage units 13 and 15. The latter operation necessary in the case of newly inserting a shot in shot sequence especially requires enormous time and labor and therefore there has been a strong demand for a system and method capable of facilitating such insert edit.